Results of Commissioning experiments for the NIF Optical Thomson Scattering diagnostic a)
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Swadling, G. F.↗
Engineering topics
Manuel, A. M.
Publications and source records attributed to Manuel, A. M..
Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility
An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. We report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ{sub 0} = 210 nm) will be used to Thomson scatter from electron plasma densities of ∼5 × 10{sup 20} cm{sup −3} while a 3ω probe will be used for plasma densities of ∼1 × 10{sup 19} cm{sup −3}. The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
The design of the optical Thomson scattering diagnostic for the National Ignition Facility [The preliminary design of the optical Thomson scattering diagnostic for the National Ignition Facility]
Here, the National Ignition Facility (NIF) is a 192 laser beam facility designed to support the Stockpile Stewardship, High Energy Density and Inertial Confinement Fusion (ICF) programs. We report on the design of an Optical Thomson Scattering (OTS) diagnostic that has the potential to transform the community’s understanding of NIF hohlraum physics by providing first principle, local, time-resolved measurements of under-dense plasma conditions. The system design allows operation with different probe laser wavelengths by manual selection of the appropriate beam splitter and gratings before the shot. A deep-UV probe beam (λ 0 -210 nm) will be used to optimize the scattered signal for plasma densities of 5 × 10 20 electrons/cm 3 while a 3ω probe will be used for experiments investigating lower density plasmas of 1 × 10 19 electrons/cm 3 . We report the phase I design of a two phase design strategy. Phase I includes the OTS telescope, spectrometer, and streak camera; these will be used to assess the background levels at NIF. Phase II will include the design and installation of a probe laser.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
ARC Stray Light Mitigation
The National Ignition Facility (NIF) is the world’s largest and most energetic laser system, located at Lawrence Livermore National Laboratory (LLNL). It is designed to study inertial confinement fusion and to conduct numerous other experiments. NIF has 192 laser beams that are directed at a small targets located at the center of a 5-m radius spherical vacuum chamber. Currently, four of these 192 beamlines (“one quad”) are undergoing modification to achieve peak power exceeding 10 15 Watts. Though the beams will have about the same energy as other NIF beams, the pulses will be compressed in time to achieve such high peak powers. This new petawatt-class laser, called Advanced Radiographic Capability (ARC), will be the world’s highest-energy, ultra-short-pulse laser and will be used to produce x-rays for backlighting NIF experiments. The 192 laser beams travel about 1.5 km in optical path length down the NIF beamline to the target chamber. It is only in the last few dozen meters, just before entering the target chamber, where the ARC quad is picked-off from the main beamline to enter a compressor vessel to decrease the pulse length and then the parabola vessel to point and focus the light onto the backlighter target.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗